Communications system

ABSTRACT

A system is disclosed in which a mobile communication device establishes device-to-device (D2D) communication with another mobile communication device, and searches for a communication network whilst engaged in the D2D communication. When it finds a communication network, the mobile communication device indicates that it is engaged in the D2D communication. The mobile communication device continues, or does not continue, the D2D communication based on an authorisation by the communication network.

TECHNICAL FIELD

The present invention relates to a communications system and to partsand methods thereof. The invention has particular but not exclusiverelevance to wireless communications systems and devices thereofoperating according to the 3GPP standards or equivalents or derivativesthereof.

BACKGROUND ART

Wireless communications systems enable users of User Equipment (UE) tocommunicate with other such users via one of a number of base stationsand a core network. Typically, the UEs are mobile terminals, such ascellular telephones and the like. In an active or connected state a UEis registered with the network and has a Radio Resource Control (RRC)connection with a base station so that the network knows to which basestation (or cell thereof) the UE belongs and can transmit data to andreceive data from the UE. The UE also establishes a default EvolvedPacket System (EPS) Bearer to an endpoint beyond the base station,typically a gateway, in the Enhanced Packet Core (EPC) network, or corenetwork for short. An EPS Bearer (which also includes Radio Bearer (RB)element between each UE and their respective serving base station)defines a transmission path through the network and assigns an IPaddress to the UE, at which it can be reached by other communicationdevices, such as another UE. An EPS Bearer also has a set of datatransmission characteristics, such as quality of service, data rate andflow control parameters, which are defined by the subscriptionassociated with the UE and are established by the Mobility ManagementEntity (MME) upon registration of the UE with the network.

The EPS Bearer is thus managed by the MME, which signals to the UE whenit needs to activate, modify, or deactivate a particular EPS Bearer. TheRadio Bearer is managed by the base station (which might further becontrolled by the MME). Thus there are always two connections betweenthe UE and the communication network: one for the user data transmittedusing the established EPS bearer (also known as the user plane) andanother one for managing the EPS Bearer and its elements (also known asthe control plane). Further details of the EPS Bearer architecture canbe found in 3GPP TS 23.401 V11.2.0 and 3GPP TS 36.300 V11.2.0, thecontents of which are hereby incorporated by reference.

As part of the Long Term Evolution (LTE) Of UTRAN (UMTS TerrestrialRadio Access Network) referred to as E-UTRAN, there are plans tointroduce a feature of direct device-(o-device (D2D) communication whenthe UE can communicate user data to another UE that is within thetransmission range of the first UE without the need to use LTE networkresources. This direct communication would result in better utilizationof the available resources, especially on the radio interface, wherethese are limited.

D2D services might be particularly beneficial for users of professionalmobile radio (PMR) networks, such as Terrestrial Trunked Radio (TETRA),and the like. Since PMR networks are mainly used by government agencies,emergency services, (police threes, fire departments, ambulance), railtransportation staff, transport services and the military, D2D voiceand/or data services may be used:

-   -   to ensure increased resilience in case of network failure by        using direct mode as a fall-back solution;    -   to support reliable communication between mobile telephones in        areas where network coverage is normally not required/provided;        and    -   to create person-to-person or person-to-group communications in        areas without network coverage at all, such as large buildings,        tunnels, basements, etc.

Although in LTE the D2D communication is predominantly controlled by thenetwork operator (i.e. the setting up of direct radio bearers betweentwo user devices is executed based on control parameters received fromtheir respective serving base stations), in some cases (e.g. for usersof PMR) it might be beneficial to allow user devices to initiate D2Dcommunication with each other without any network provided controlparameter. This may be beneficial (or even necessary) in some of theabove mentioned cases, especially when a D2D communication sessioninvolves at least one user device that is operating outside the coveragearea of LTE base stations and hence would not able to obtain D2D controlinformation from the network. Therefore, if such D2D capable userdevices are within communication distance from each other, they mightset up a D2D communication channel between them without the LTE networkprovided control parameters.

However, when user devices are operating a D2D channel that has been setup without control parameters provided by the network, a particularproblem might arise that their transmissions over this D2D channel mightcause harmful interference to nearby LTE devices (and vice versa). Suchinterference is even more likely to happen when the D2D channel (atleast partially) overlaps with the LTE channels (i.e. the licensed LTEspectrum) used by the network or when these user devices (re)enter thecoverage area of an LTE base station whilst still transmitting on theD2D channel.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to reduce or eliminate theinterference resulting from D2D transmission whilst still making itpossible for D2D capable user devices to communicate with each othereven in the absence of an LTE network.

Accordingly, in one aspect the invention provides a mobile communicationdevice for communicating using device-to-device (D2D) communication, themobile communication device comprising: means for establishing D2Dcommunication, with another mobile communication device; means forsearching for a communication network whilst communicating with theother mobile communication device using said D2D communication; meansfor providing, to a communication network and responsive to saidcommunication network being found during said searching, an indicationthat the mobile communication device is engaged in said D2Dcommunication; means for receiving a response to the indication fromsaid communication network; and wherein the mobile communication deviceis operable to continue, or not continue, the D2D communication based onthe response.

The means for establishing D2D communication might be operable tocoordinate the presence of gaps in said communication, and the searchingmoans might be operable to monitor for the communication network duringthe gaps in said communication.

The receiving means might be operable to receive a response comprisinginformation for authorising the D2D communication and the mobilecommunication device might be operable to continue D2D communicationbased on the response.

The mobile communication device might be operable to cease said D2Dcommunication in the absence of the response within a defined timeperiod.

The response might comprise reconfiguration information and the mobilecommunication device might be operable to reconfigure said D2Dcommunication based on the reconfiguration information. In this case,the mobile communication device might be operable to reconfigure saidD2D communication to be controlled via the communication network basedon the reconfiguration information.

The receiving means might be operable to receive a response comprisinginformation indicating that said D2D communication has not beenauthorised and the mobile communication device might be operable tocease said D2D communication based on the response.

The mobile communication device might be operable to continue said D2Dcommunication in the absence of the response.

The response might comprise reconfiguration information and the mobilecommunication device might be operable to reconfigure communicationbetween the mobile communication devices to use a communication protocolother than a D2D based communication protocol based on thereconfiguration information. In this case, the mobile communicationdevice might be operable to reconfigure said communication between themobile communication devices to use a cellular communication protocol(e.g. a long term evolution (LTE) based communication protocol).

The mobile communication device might further comprise means forestablishing a connection with the communication network when thecommunication network has been found. In this case, the means forproviding an indication might be operable to provide the indication aspart of said establishing a connection. Alternatively, the means forproviding an indication might be operable to provide the indicationusing the connection once established.

The means for establishing a connection might be operable to establish aRadio Resource Control (RRC) protocol connection. The means forestablishing a connection might be operable to send at least one of an‘RRC Connection Setup Request’ message and an ‘RRC Connection SetupComplete’ message as part of said establishing a connection and themeans for providing an indication might be operable to provide theindication in the at least one said ‘RRC Connection Setup Request’message and ‘RRC Connection Setup Complete’ message.

The response might comprise at least one RRC protocol message, forexample, at least one ‘RRC Connection Configuration’ message.

The indication providing means might be operable to provide furtherinformation identifying at least one of: a channel and/or a frequencyused by said D2D communication; an interference level; an amount of datato be transmitted using said D2D communication; a priority level of saidD2D communication; the mobile communication device; and/or the othermobile communication device. The further information might be providedin response to receiving a request from a node of the communicationnetwork.

The mobile communication device might be one of a mobile telephone, alaptop computer, and a personal digital assistant.

In another aspect the invention provides a communication node in acommunication network for controlling a mobile communication deviceengaged in a device-to-device (D2D) communication, the communicationnode comprising: means for obtaining an indication that the mobilecommunication device is engaged in D2D communication; means fordetermining, based on said obtained indication, whether or not said D2Dcommunication should be authorised; and means for providing to themobile communication device, in response to said indication, informationindicating that said D2D communication has been authorised orinformation indicating that said D2D communication has not beenauthorised.

The communication node might further comprise means for configuring themobile communication device. The configuring means might be operable toreconfigure said D2D communication to be controlled via thecommunication network. The configuring means might be operable toreconfigure said communication between the mobile communication devicesto use a communication protocol other than a D2D based communicationprotocol. In this case, the configuring means might be operable toreconfigure said communication between the mobile communication devicesto use a cellular communication protocol (e.g. a long term evolution(LTE) based communication protocol).

The communication node might further comprise means for establishing aconnection with the mobile communication device and the obtaining meansmight be operable to obtain the indication during or after saidestablishment of the connection.

The obtaining means might be operable to obtain, from at least one othercommunication node connected to the communication node, informationrelating to said D2D communication. In this case, the obtaining meansmight be operable to obtain information data relating to said D2Dcommunication before the establishment of said radio connection.

The obtaining means might be operable to obtain information relating toa level of interference resulting from said D2D communication and thedetermining means might determine that said D2D communication should notbe authorised when said level of interference is above a predeterminedthreshold.

The obtaining means might be operable to establish a Radio ResourceControl (RRC) protocol connection with the mobile communication deviceand/or another mobile communication device. The obtaining means might beoperable to receive at least one RRC protocol message. The at least oneRRC protocol message might comprise at least one of an ‘RRC ConnectionSetup Request’ message and an ‘RRC Connection Setup Complete’ messageand the means for obtaining an indication might be operable to obtainthe indication from the at least one said ‘RRC Connection Setup Request’message and ‘RRC Connection Setup Complete’ message.

The providing means might be operable to send at least one RRC protocolmessage. In this case, the at least one RRC protocol message mightcomprise at least one ‘RRC Connection Configuration’ or ‘RRC ConnectionReconfiguration’ message.

The communication node might further comprise means for obtaininginformation related to said D2D communication from at least one of: themobile communication device engaged in said D2D communication; anothermobile communication device which is not engaged in said D2Dcommunication; and another communication node in the communicationnetwork. In this case, the means for obtaining information related tosaid D2D communication might be operable to send a request and receive aresponse to the request.

The communication node might be one of a base station, a mobilitymanagement entity, and a home subscriber server.

In a third aspect the invention provides a mobile communication devicefor assisting a communication node managing radio channels used by adevice-to-device (D2D) communication, the mobile communication devicecomprising: means for monitoring radio transmissions indicative of apossible D2D communication between other mobile communication devices;and means for providing information relating to said possible D2Dcommunication to the communication node and responsive to the monitoringmeans detecting radio transmissions indicative of said possible D2Dcommunication. In this case, the mobile communication device might beoperable to perform said monitoring in response to a request form thecommunication node. The mobile communication device might furthercomprise means for establishing D2D communication, with another mobilecommunication device.

The invention also provides corresponding methods and a systemcomprising the above mobile communications device and the abovecommunication node.

A further aspect of the present invention provides a computer programproduct comprising computer implementable instructions for causing aprogrammable computer device to become configured as a mobilecommunications device or a communication node as described above. Thecomputer software products may be provided on a carrier signal or on arecording medium, such as a CD, DVD or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 illustrates schematically a cellular telecommunications system towhich embodiments of the invention may be applied;

FIG. 2 is a functional block diagram illustrating some of thefunctionality of a mobile telephone forming part of the system shown inFIG. 1;

FIG. 3 is a functional block diagram illustrating some of thefunctionality of a base station forming part of the system shown in FIG.1;

FIG. 4 is a timing diagram illustrating the way in which the basestation authorises an already set up D2D connection;

FIG. 5 is a timing diagram illustrating the way in which the basestation instructs the mobile telephone, to switch from an already set upD2D service to an LTE service; and

FIG. 6 is a timing diagram illustrating the way in which the basestation obtains information relating to a D2D service from a mobiletelephone.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS Overview

FIG. 1 schematically illustrates a cellular communication network 1 inwhich users of user equipment such as mobile telephones (MT) 3-1 to 3-3can communicate with each other and other users via a base station 5 anda core network 7. As those skilled in the art will appreciate, whilstthree mobile telephones 3 and one base station are illustrated in FIG. 1for illustration purposes, additional devices and base stations may bepresent in a deployed system. Conventionally, when two mobile telephones3 are in communication with each other, user plane data is routed fromthe first mobile telephone 3 to its base station 5, through the corenetwork 7, one or more gateway(s) 8, back to the base station 5 servingthe second mobile telephone 3, then to the second mobile telephone 3(and similarly for user plane data sent in the opposite direction). Inthis example, the communication network is a Long Term Evolution (LTE)network comprising a so called Evolved UMTS Terrestrial Radio AccessNetwork (E-UTRAN). The core network 7 in this example is an EvolvedPacket Core (EPC) network which includes, amongst other things, amobility management entity (MME) 9 and a home subscriber server (HSS)10.

The communication paths of the cellular network described above ensurethat data is transmitted between the mobile telephones 3 in compliancewith the relevant subscription parameters, any service criteria requiredby the mobile telephones 3, and the security criteria imposed by thenetwork. However, such an arrangement can be wasteful of resources inthe base station 5, and in the core network 7, when, for example, thetwo mobile telephones 3 are within radio communications range of eachother and a direct user plane communication link can be used instead.Moreover, in some cases, one or both of the mobile telephones 3 might belocated outside the coverage area of an appropriate cellular network.

Therefore, in this example, the mobile telephones 3-1 and 3-2 arebeneficially able to set up a device-to-device communication pathbetween them without involving the cellular network thereby alleviatingthe pressure on network resources without the involvement of thecellular network.

The mobile telephones 3-1 and 3-2, when involved in D2D communication,are also capable of searching for a cellular network to establish an RRCconnection with (for example, when the D2D communication is establishedwhen there is no network coverage). Once a cellular network (e.g. a cellof base station 5) is detected, the mobile telephone 3-1 establishes anRRC connection with the cellular network by sending, an appropriate RRCrequest to the base station 5. Using the established RRC connection, themobile telephone 3-1 informs the base station 5 (or another networkelement, such as the mobility management entity 9 via the base station5) that the mobile telephone is involved in a D2D service with anothermobile telephone 3-2.

This beneficially allows the network to take action to mitigate againstpotential interference to other devices operating within the cellularnetwork (such as mobile telephone 3-3 or the base station 5) that mightarise due to the D2D transmission between the mobile telephones 3.

Specifically, in this example, the base station 5 receiving theindication that the mobile telephone 3 is involved in a D2D serviceevaluates the received information and determines whether or not theindicated D2D service is to be maintained or another communicationtechnology (e.g. an LTE cellular based technology) is to be usedinstead. The base station 5 (or another network entity, such as the MME9) may check, for example, whether the interference unused by theindicated D2D service is below a predetermined threshold, whether theparameters used in the D2D service comply with the applicable networkpolicies, whether communication between the mobile telephone 3 and theother communication node can or should be provided in any way other thana D2D service, etc.

If the on-going D2D service is authorised, the base station 5 sends anRRC response message to the mobile telephone 3, informing the mobiletelephone 3 that it can continue its D2D transmissions. Besides theauthorisation indication, the base station 5 might also include in thisRRC message additional control parameters in order to instruct themobile telephone 3 to adjust its D2D operation to avoid or eliminateinterference, if necessary.

If the on-going D2D service is not authorised by the network, the basestation 5 includes an indication to this effect in an associated RRCmessage it sends to the mobile telephone 3. Advantageously, the basestation 5 might also instruct (within the same or in a subsequentmessage) the mobile telephones 3 to set up a cellular communicationchannel between them, to which communication channel the current D2Dcommunication session may be ‘handed over’. In this way the base station5 can ensure service continuity for the mobile telephones 3 within itscells even for those communication sessions that have started as a D2Dservice and/or started while (at least one of) the mobile telephones 3were located outside the coverage area of the cellular network.

In the system illustrated in FIG. 1, in order to evaluate the effect ofthe D2D service on the cellular network performance, the base station 5takes into account signal measurement results from other communicationnodes within its cell(s), such as mobile telephone 3-3 or the like.

For example, mobile telephone 3-3 is configured to provide periodicsignal measurement reports and/or indicate unusual interference (e.g.that might arise clue to an on-going D2D service that has not beenauthorised by the cellular network). Using the received indicationrelating to the on-going D2D service, the base station 5 can takepreventive actions, e.g. by allocating different resources to the mobiletelephone 3-3 on other, non-interfering, cellular channels, and keep thechannel(s) used by the D2D service reserved for mobile telephones 3-1and 3-2 as long as the interference exists (e.g. the interference levelis determined to be higher than a predetermined threshold level).

Moreover, when the mobile telephones 3-1 and 3-2 are located outside thecoverage area of the cellular network, the measurement reports providedby mobile telephone 3-3 are beneficially used as an early indication ofon-going D2D transmissions near the edge of the cell(s) of the basestation 5. Therefore, when the mobile telephone 3-1 (or 3-2) that isinvolved in a D2D service subsequently establishes an RRC connectionwith the base station 5, the D2D service might be authorised without thebase station having to allocate resources to these mobile telephones, asthe required resources have been reserved for them already.

As will become clear from the following description, once a decision istaken that a D2D connection between two mobile telephones 3 isauthorised, the base station triggers the necessary signalling (e.g.RRC) that will inform the mobile telephones 3 to continue communicatingusing an existing D2D communication bearer. However, management of theD2D bearer transfers from the mobile telephones 3-1, 3-2 to the cellularnetwork (e.g. as an EPS bearer for which a dedicated Traffic FlowTemplate (TFT) is assigned). Therefore, in this example, control planerelated to the D2D service is switched over to the cellular network atleast whilst the mobile telephones 3 are within the coverage area of thenetwork.

This approach beneficially allows D2D communications between the twomobile telephones 3 to be set up without involving a base station 5whilst also minimising harmful interference caused to the cellularnetwork. By establishing an RRC connection with the base station 5, i.e.when entering the coverage area of the cellular network 1, the mobiletelephone 3-1 establishes a control plane connection with the corenetwork 7 to handle its communication with the other communicationnodes. However, in this case, the mobile telephone 3-1 does not need towait until an RRC connection is established in order to start a D2Dservice with another mobile telephone 3-2, and it can also fall-back tosuch a D2D service when it loses connection with the cellular network.

The advantages of the embodiments include that, as long as theyare/remain within the coverage area of the cellular network,communication services used by the mobile telephone 3 are controlled bythe network (e.g. base station 5) but when they are outside of thecellular network, and still within communication distance from eachother, the mobile telephones 3 can establish a D2D service withouthaving to rely on the base station 5. Additionally, the mobiletelephones 3 (if necessary) might use communication channels that areotherwise licensed to—and hence reserved for—communication devicescontrolled by the communication network 1 regardless whether or not theyare operating within a cell operated by one of the base stations 5.

Mobile Telephone

FIG. 2 shows a functional block diagram of a mobile telephone 3 shown inFIG. 1. As shown, the mobile telephone 3 has a transceiver circuit 3that is operable to transmit signals to and to receive signals fromabase station 5 via one or more antenna 33. The mobile telephone 3 has acontroller 37 to control the operation of the mobile telephone 3. Thecontroller 37 is associated with a memory 39 and is coupled to thetransceiver circuit 31. Although not necessarily shown in FIG. 2, themobile telephone 3 will of course have all the usual functionality of aconventional mobile telephone 3 (such as a user interface 35) and thismay be provided by any one or any combination of hardware, software andfirmware, as appropriate. Software may be pre-installed in the memory 39and/or may be downloaded via the telecommunication network or from aremovable data storage device (RMD), for example,

The controller 37 is configured to control overall operation of themobile telephone 3 by, in this example, program instructions or softwareinstructions stored within memory 39. As shown, these softwareinstructions include, among other things, an operating system 41, acommunications control module 43, a D2D control module 45, a cellularnetwork monitoring module 46, a D2D state determination module 47, and areporting module 49.

The communications control module 43 is operable to handle (e.g.generate, send and receive) control signals for controlling theconnections between the mobile telephone 3 and other mobile telephones 3or various network nodes, such as the base station 5. The communicationscontrol module 43 also controls the separate flows of uplink data andcontrol data that are to be transmitted to the other mobile telephone 3or to the base station 5.

The D2D control module 45 is operable to generate and provideinstructions for the communications control module 43 for setting up adevice-to-device communication path with another mobile telephone 3. TheD2D control module 45 is also operable to ensure that transmission gapsare provided in the D2D service, at least whilst the mobile telephone 3is operating outside the coverage area of an cellular network or untilthe D2D service has been authorised by the base station 5.

The cellular network monitoring module 46 is operable to search foravailable cellular networks that the mobile telephone 3 can connect toin order to obtain anthorisation for its on-going D2D communication.

The D2D state determination module 47 is operable to determine whetheror not the mobile telephone 3 is utilising a D2D service for its voiceand/or data communication. When there is a change in the state of theD2D service, the D2D state determination module 47 informs the reportingmodule 49 about the current D2D state (e.g. active or inactive).

The reporting module 49 is operable to generate and send information tothe base station 5 relating to the current D2D state of the mobiletelephone 3. Typically, such D2D state indication is provided to thebase station 5, via the transceiver circuit 31, upon the mobiletelephone 3 establishing an RRC connection with the base station 5 (inthis ease e.g. a ‘D2D state: active’ indication is provided) and when anauthorised D2D service is terminated ‘D2D state: inactive’ indication isprovided).

Base Station

FIG. 3 shows a functional block diagram of the base station 5 shown inFIG. 1. As shown, the base station 5 has a transceiver circuit 51 fortransmitting signals to and for receiving signals from the mobiletelephones 3 via one or more antenna 53, a core network interface 55 fortransmitting signals to and for receiving signals from devices in thecore network 7 (such as the mobility management entity 9). The basestation 5 has a controller 57 for controlling the operation of the basestation 5. The controller 57 is associated with a memory 59. Althoughnot necessarily shown in FIG. 3, the base station 5 will of course haveall the usual functionality of a cellular telephone network base stationand this may be provided by any one or any combination of hardware,software and firmware, as appropriate. Software may be pre-installed inthe memory 59 and/or may be downloaded via the communication network 1or from a removable data storage device (RMD), for example.

The controller 57 is configured to control the overall operation of thebase station 5 by, in this example, program instructions or softwareinstructions stored within memory 59. As shown, these softwareinstructions include, among other things, an operating system 61, acommunications control module 63, a D2D control module 65, aninterference handling module 67, and a D2D authorisation module 69.

The communications control module 63 is operable to handle (e.g.generate, send and receive) control signals for the mobile telephones 3and other network entities that are connected to the base station 5. Thecommunications control module 63 is also operable to manage RRCconnections for the mobile telephones 3 that are attached to the networkvia the base station 5.

The D2D control module 65 is operable to instruct the communicationscontrol module 63 to send the signalling messages required to configureor reconfigure (i.e. setup or modify) device-to-device communicationlinks between mobile telephones 3.

The interference handling module 67 is operable to evaluate interferencerelated indications (e.g. channel state information (CSI) and/or channelquality indication (CQI) reports) relating to the mobile telephones 3served by the base station 5 and to take corrective actions in order toreduce the interference experienced by these mobile telephones 3.

The D2D authorisation module 69 is operable to authorise and, ifnecessary, reconfigure D2D communications by the mobile telephones 3associated with this base station 5. The D2D authorisation module 69evaluates the D2D state indications received from the mobile telephones3 and interfaces with the interference handling module 67 to determinethe effect of the indicated D2D state on the interference levels withinthe cell(s) of the base station 5.

In the above description, the mobile telephone 3 and the base station 5are described for ease of understanding as having a number of discretemodules (such as the communications control modules and the D2D controlmodules). Whilst these modules may be provided in this way for certainapplications, for example where an existing system has been modified toimplement the invention, in other applications, for example in systemsdesigned with the inventive features in mind from the outset, thesemodules may be built into the overall operating system or code and sothese modules may not be discernible as discrete entities. These modulesmay also be implemented in software, hardware, firmware or a mix ofthese.

Operation—D2D Communication Continues

A more detailed description will now be given (with reference to FIG. 4)of the scenario discussed above where a D2D communications link isestablished between two mobile telephones 3-1 and 3-2 which issubsequently authorised by the cellular network.

Initially, as shown in step s400, the mobile telephones 3-1 and 3-2establish a device-to-device communication path, using their respectiveD2D control modules 45, in order to communicate with each other. At thisphase, the mobile telephones 3 (or at least one of them) are locatedoutside the coverage area of the cellular network. In step s401, themobile telephones 3 start using the D2D service for voice and/or datacommunication between them.

After initiation of the D2D service, as shown in step s402, the D2Dcontrol modules 45 coordinate the mobile telephones' D2D transmissionsuch that there are transmission gaps (e.g. ‘silent’ periods) in the D2Dcommunication when the mobile telephones 3-1, 3-2 do not transmit datato provide opportunities for the mobile telephones 3-1, 3-2 to monitorfor the presence of the cellular communication network and performmeasurements. This step also comprises exchanging measurement gappattern(s) between the mobile telephones to ensure appropriatesynchronisation.

In step s403, the mobile telephones 3 begin to search for a cellularnetwork using their cellular network monitoring module 46. In thisexample, the cellular network monitoring module 46 uses a similarprocedure that is used by RRC Idle mode mobile devices when selecting asuitable cell to camp on, which will be known to those skilled in theart and will not, therefore, be described in more detail. Unlike normalidle mode search procedures which can occur, essentially, at any time),however, the cellular network monitoring modules 46 restrict their ‘idlemode’ (or ‘pseudo idle mode’) search procedures, while D2D communicationis occurring, to coincide with the above mentioned transmission gaps.

When one of the mobile telephones discovers a cellular network, in steps404, its reporting module 49 generates and sends (via transceivercircuit 51) the base station 5 an indication that the mobile telephone3-1 making the discovery is involved in a D2D communication service (instep S405).

In this example, between step s404 and step s405, the D2D controlmodules 45 coordinate the mobile telephones' transmission gaps, andadjust them if necessary, such that the gaps are sufficiently long (e.g.at least one radio-frame (or 10 ms) but preferably at least tworadio-fames (or 20 ms) in duration). This allows the mobile telephonesto read system information broadcast by the base station 5 and toexchange messages with the network in relation to the sending of the D2Dservice indication. However, the transmission gaps are kept sufficientlyshort, and with a sufficiently long period between the gaps, to ensurethat they do not have significant impact on the D2D data/voicecommunication. For example, whilst a gap duration of 6 msec might besufficient for the D2D device 3 to perform physical layer measurements,the same gap duration might not be sufficient to read the informationrequired to establish a connection with the network due to theperiodicity of system information (SI) broadcast and the time requiredto obtain the SI. Therefore, the D2D control modules 45 configure biggertransmission gaps (i.e. longer than 6 msec), for example, up to 80 msecin duration. In case of a D2D voice call service, this would mean thatthe D2D device 3 skips up to four voice packets (each one being 20 msecin duration). However, this would not be noticeable to the user of theD2D device For other applications than voice (e.g. a D2D data service)the D2D control modules 45 might configure the same 80 msec gapduration. Alternatively, the D2D device might configure a different gapduration (e.g. longer than 80 msec) and, if necessary, rely on higherlayer retransmission (e.g. TCP) of any skipped data packets.

In this example, the D2D service indication is included in the first RRCmessage sent from the mobile telephone 3-1 (e.g. an ‘RRC ConnectionSetup Request’ message) and is sent during one of the silent periods ofthe D2D service (in order to avoid interference between the mobiletelephone's D2D and cellular communications). The reporting module 49indicates the on-going D2D service, for example, by specifying a ‘causevalue’ e.g. the ‘establishment cause’) within the ‘RRC Connection SetupRequest’ message. Thus, the mobile telephone 3-1 informs the basestation 5 that the reason for establishing the RRC connection is toinform the base station 5 that the mobile telephone 3-1 is involved inD2D service.

It will be appreciated that, alternatively, the reporting module 49might include a D2D service indication in a message other than the firstRRC message sent from the mobile telephone (e.g. the ‘RRC ConnectionSetup Complete’ message). In this case, the reporting module 49 mightalso include additional information identifying the type of D2D serviceused (e.g. duplex/half-duplex, FDD/TDD, etc.) and any furtherinformation (e.g. channels used, data rate, transmission power, UE IDs,priority, etc.) that can be used to assist the base station in itsdecision to authorise the D2D service. This will allow the base station5 to prioritize certain services over others and avoid misuse of theservice by mobile phone applications.

As shown in steps s404′ and 405′, if the other mobile telephone 3-2finds a cellular network, it also generates and sends a D2D serviceindication to the base station 5 in addition to (or instead of) theindication by the first mobile telephone 3-1. Although not shownseparately, the mobile telephone sending the first indication to thebase station 5 might also inform the other mobile telephone about thisindication (e.g. using the D2D service between them) so that only one ofthem has to establish an RRC connection with the network for indicatingthe on-going D2D service. In this way, provision of redundantinformation and excessive signalling can be avoided. Alternatively,since at this point both mobile telephones 3-1 and 3-2 might still belocated relatively far from the base station 5 (and hence might not beable to reliably transmit data to the base station 5), it might bebeneficial if both mobile telephones 3 send an indication to the basestation 5, by way of redundancy, to ensure safe receipt thereof.

In either case, at step s409, the D2D authorisation module 69 of thebase station 5 evaluates the received information relating to theon-going D2D service which has been set up without involving thecellular network in order to determine whether or not continuation ofthe D2D service should be authorised and/or whether provision of the D2Dservice should be reconfigured.

Thus, in this step, the D2D authorisation module 69 determines whetheror not this D2D service is allowed to continue, e.g. by estimating alevel of interference caused by the D2D service to other, networkauthorised communications within the cell(s) controlled by this basestation 5. In order to do this, the D2D authorisation module 69 may takeaccount of other relevant information provided internally from the othermodules of the base station 5 (such as the communications control module63, the D2D control module 65, and the interference handling module 67)or externally from other network nodes (e.g. the MME 9, the HSS 10 orthe like). For example, the D2D authorisation module 69 may take accountof information identifying a priority level for the call (e.g. a highpriority level being assigned to an emergency services related call)and/or to make sure that only those D2D services are authorised that arein compliance with applicable network policies (e.g. allowing specificsubscriber groups, such as emergency services or specific tariff groups,to have preferential D2D access).

In this example, the D2D authorisation module 69 determines that the D2Dcommunication is allowed to continue, and thus it generates and sends,in step s411 (and/or 411′), a message to the Mobile telephone 3-1(and/or mobile telephone 3-2), which message authorises the D2D servicewith the other mobile telephone to continue. The base station 5 is thusable to reserve the communications resources being used for the D2Dcommunication (if the base station has been provided with informationidentifying those resources) to avoid those resources being used forother communications (e.g. cellular) in the vicinity of the D2Dcommunications thereby avoiding associated interference.

As shown in step s415, the mobile telephones 3 continue their D2Dtransmission, which has now been authorised by the cellular network.

If necessary, the D2D control module 65 of the base station 5 might alsoinstruct the mobile telephones 3-1 or 3-2 to modify their D2D service tohelp avoid or alleviate interference, e.g. by providing updated D2Dcontrol parameters in the authorisation message sent at either one ofsteps s411 and s413, or in a separate message (not shown).Alternatively, or additionally, the D2D control module 65 of the basestation 5 might instruct one or more other mobile telephones and/or basestations, using the cellular network, to reconfigure theircommunications to help avoid or alleviate interference.

When in step s417, the D2D service terminates (e.g. due to the user ofeither mobile telephone 3-1 or 3-2 ending the D2D service or the mobiletelephones 3 running out of data to be sent), which is detected by theD2D state determination module 47, the cellular network monitoringmodule 46 checks whether the mobile telephone 3-1 is still within thecoverage area of the cellular network. If the cellular networkmonitoring module 46 finds that the mobile telephone 3-1 is stillcamping on a cell of the base station 5, it triggers the reportingmodule 49 to generate and send (as shown in step s419) an indication tothe base station 5 that the previously authorised D2D service has beenterminated. Alternatively, or additionally, the second mobile telephone32 might also generate and send this indication, as illustrated in steps419′.

In step s423, the base station 5 evaluates the received indication and,if necessary, allocates the resources (e.g. channels) previously used by(and possibly reserved for) the D2D service to other communicationdevices as appropriate. Since the base station 5 is now aware of thetermination of the D2D service, it also knows that the frequenciespreviously affected by the D2D service would no longer suffer harmfulinterference from mobile telephone 3-1 or 3-2.

Advantageously, therefore, the manner in which the D2D service isauthorised by the base station 5 can be used to help alleviate, oravoid, interference caused by the transmissions of mobile telephones 3-1and 3-2 to the other communication nodes in their vicinity.

Thus, the mobile telephones 3 are able to communicate with each othereven in the absence of an cellular network (e.g. in large buildingswhere there is no coverage such as in tunnels, basements, undergroundgarages etc, to provide person-to-person communications). However, oncethey are within range of a network, it is ensured that their on-goingD2D session remains in compliance with existing network policies andthat harmful interference is reduced or eliminated.

Operation—D2D Communication Transfers to Cellular Communication

A more detailed description will now be given (with reference to FIG. 5)of the scenario discussed above where a D2D communications link isestablished between two mobile telephones 3-1 and 3-2, and which issubsequently replaced by a cellular service.

Steps s500 to s507 are similar to steps s400 to s405′ of FIG. 4,respectively. However, instead of authorising the already existing D2Dservice, at step s509 the D2D authorisation module 69 of the basestation 5 determines that the mobile telephones 3-1 and 3-2 shouldswitched over to a cellular service instead. This may be necessary, forexample, when the interference caused by the D2D service is above apredetermined threshold (as indicated by the interference handlingmodule 67), or when there is a need to provide additional functions thatare not available using the D2D service (e.g. security relatedfunctions, subscription related functions, positioning functions, poweroptimisation, or the like).

In this step (i.e. s509), the base station 5 might also verify that bothmobile telephones involved in the D2D service are reachable via thecellular network before trying to switch their communications over to acellular based service. This verification step might comprise, forexample, waiting for both mobile telephones to establish an RRCconnection, send a D2D service indication, or respond to a pagingmessage by the base station.

Authorisation of any on-going D2D service may depend on the networkoperator's policy. If the on-going D2D service is indicated to becritical, then the network will authorise the service to continue (forexample, D2D communications by fire and/or emergency personnel).However, regardless of the type or importance of the D2D service, it isimportant that the network is made aware of an on-going D2D servicewithin its coverage area. For example, LTE networks (which are operatedas commercial systems) need to be aware of communications by userequipment that may be misusing the D2D service, cause interference, andthereby result in a loss of revenue for the network operator.

After the base station 5 determines that a cellular service should beused instead of indicated D2D service, at step s511 (and/or at step511′), its D2D authorisation module 69 generates and sends to the mobiletelephone a message (or series of messages) instructing it to switchover to a cellular service. The message(s) also include(s) the necessarycontrol parameters provided by the communications control module 63(e.g. resource allocation, quality of service, modulation and the like)for the mobile telephones 3 to be able to use a cellular communicationpath via the base station 5.

In step s515, the mobile telephones 3 set up an LTE communication path(using their respective communications control modules 43) and startcommunicating with each other via the cellular network. Next, in steps517, the D2D control module 45 terminates the D2D service between thetwo mobile telephones 3.

One benefit associated with this alternative is that the mobiletelephones 3 are able to communicate with each other even in the absenceof a cellular network. However, once they enter the coverage area of anetwork, they switch over to cellular services and might thus benefitfrom a more reliable service and/or a broader range of services thanwould be available using the D2D service.

Operation—Indirect Detection of D2D Communication

A more detailed description will now be given (with reference to FIG. 6)of the scenario discussed above where a mobile telephone 3-3 detects andindicates an on-going D2D communication, that it is not involved in, tothe base station 5.

In this case, at step s601, the base station 5 requests the mobiletelephone 33 to perform measurements for use in identifying the possiblepresence of D2D transmissions that might cause interference tocommunications in the cellular network. Although preferably this mobiletelephone 3-3 is also capable of D2D transmissions, in this example itis not involved in any D2D service. The request sent at step s601 may,for example, be an ‘RRC UE information Request’ message which is definedin 3GPP TS 36.331 v 11.2.0, the contents of which are incorporatedherein by reference.

Next, in step s603, the mobile telephone 3-3 performs the requestedmeasurements (effectively ‘looking’ for a D2D transmission). This stepmay be performed once, periodically, or continuously, depending on therequest received at the previous step.

The reporting module 49 of the mobile telephone 3-3 generates and sends,in step s605, a measurement report that effectively acts as anindication, to the base station 5, whether or not a D2D service islikely to be occurring in the vicinity. This message is, for example, an‘RRC UE Information Response’ message which is sent in response to therequest at step s601. Additionally, the reporting module 49 mightinclude interference information in this message or in a subsequent one(not shown) to indicate to the base station 5 whether or not the mobiletelephone's transmissions are being adversely affected by a potentialD2D service.

The information provided by the reporting module 49 might, for example,include information on uplink and downlink channel quality and RadioResource Management (RRM) measurements.

The approach described with reference to FIG. 6 is particularlybeneficial when both uplink and downlink use the same frequency spectrum(e.g. in case of LTE Time-Division Duplex (TDD) transmissions) as theD2D services. However, the approach is also beneficial in the case whenat least one of the uplink and downlink resources coincides withresources used by the D2D service (e.g. in case of Frequency-DivisionDuplex (FDD) transmissions).

Upon receipt, of the measurements related to the potential presence of aD2D service, by the base station 5, the interference handling module 67evaluates the received information, in step s609, to determine if a D2Dservice appears to be occurring. The base station 5 can thus performcorrective actions in order to reduce or eliminate any harmfulinterference caused by a detected D2D service. For example, theinterference handling module 67 might mark the channels used by theon-going D2D service as being reserved (in use) or make them availablefor those services only that do not require interference-freetransmission (e.g. services that are not time-critical).

In step s611, the base station 5 assigns non-interfering communicationresources to the mobile telephone 3-3 thereby alleviating or eliminatingassociated interference.

In this example, the mobile telephone 3-3 continues to perform therequested measurements in step s617, and provides these to the basestation in step S619. If the measurements indicate that a previouslydetected D2D service has terminated or its potential interferencehasbecome lower than a predetermined threshold the base station 5detects this at S623.

Upon determination of potential D2D related interference ceasing, instep s623, the base station 5 evaluates the received information andadjusts its operation accordingly. For example, the interferencehandling module 67 might make the channels previously used by theon-going D2D service available again for time-critical services.

Modifications and Alternatives

Detailed embodiments have been described above. As those skilled in theart will appreciate, a number of modifications and alternatives can bemade to the above embodiments whilst still benefiting from theinventions embodied therein. By way of illustration only a number ofthese alternatives and modifications will now be described.

For example, it will be appreciated that the network search, asindicated at steps s403 and s503, might be performed by the mobiletelephone only once, periodically, or even continuously. Although in theabove examples the network search has been described as being performedduring the silent periods (i.e. transmission gaps) of the D2D service,it will be appreciated that the network search might be carried out evenduring D2D transmissions (i.e. outside the transmission gaps). Forexample, if the mobile telephones are communicating using a half-duplexD2D channel (either TDD of FDD), they will either transmit or receiveover the D2D channel and communication gaps may thus be provided whenthey switch between the transmit and receive mode of operation. In thiscase there may be no need to provide additional transmission gaps thanwhat is already mandated by the half-duplex D2D communication channel.For those mobile telephones that are capable of simultaneously searchingfor a cellular network and transmitting data over the D2D communicationchannel, it is not necessary to provide transmission gaps at all.Therefore, at least in the above situations, steps s402 and s502 may beomitted or might be combined with steps s400 and s500, respectively.

Furthermore, it will be also appreciated that the mobile telephone willcontinue its network search even after the base station has authorisedthe on-going D2D service. This might be necessary, e.g. in case themobile telephone needs to select a new cell to camp on (e.g. due tomovement of the mobile telephone or changes in the perceived signalquality within the current cell). The network search might be performedby a mobile phone while it is operating in the RRC Idle mode. Therefore,it will therefore be appreciated that steps s403 and s503 may beperformed independently of the D2D operation of the mobile telephone.

A skilled person would thus also understand that steps s405 and s505(also s405′ and s505′), in which the mobile telephone indicates anon-going D2D service to the base station, might be repeated every time anew cell or a new base station is found. In this case, the authorisationof the D2D service by the base station (i.e. steps s409 to s411/s411′and s509 to s511/s511′) might also be repeated every time an indicationof the on-going D2D service is received (by the same or a different basestation) or even without receiving such an indication. In onealternative, an already authorised D2D service is subsequently switchedover to a cellular service by the same or a different base station. Thisway the base station ensures that interference is kept minimised oreliminated not only at the time of receiving the D2D service indication(i.e. steps s405, s405′, s505, s505′) but continuously, even afterauthorising the D2D service. This might be particularly beneficial whenchanging signal or load conditions within the cell(s) of the basestation necessitate using a cellular service instead of the current D2Dservice.

In the above embodiments a mobile telephone involved in a D2D service isconfigured to indicate this on-going D2D service to a base station.However, it will be appreciated that the base station might receive thisindication from any other mobile telephone (i.e. one that is notinvolved in the D2D service) or via another network element (e.g. aneighbour base station or an entity in the core network).

In addition to the above scenarios, there is also the scenario where thetwo mobile telephones 3 that are communicating with each other using theD2D service find different cells to camp on which are operated bydifferent base stations (which might be also connected to different corenetworks). This might happen if, for example, the two mobile telephonesare subscribed to different network operators. The operation of such anembodiment is very similar to that illustrated in FIGS. 4 and 5, exceptthat there will also be two base stations (and possibly two corenetworks) involved in the process. However, in this case, the first basestation will authorise the D2D service for the mobile telephone it isserving and the other base station will also authorise the D2Dconnection to the other mobile telephone. In this case, the on-going D2Dservice might need to be authorised by both base stations in order tocontinue. If any of the mobile telephones receives instructions toswitch to the cellular service, the other mobile telephone also releasesthe D2D service even if this has been authorised by the other basestation.

In the above embodiment, two mobile telephones were allowed to establisha D2D connection with each other. As those killed in the art willappreciate, D2D connections may be established between three or moremobile telephones, such that the users of the mobile telephones may beconnected together in a conference call setup.

The above embodiments have described preferred ways of indicating anongoing D2D service to the base station and authorising mobile devicesto participate in such D2D service. As those skilled in the art willappreciate, other signalling messages may be used to carry the D2Dservice indication towards the base stations and the authorisationtowards the respective user devices. For example, in the abovescenarios, the D2D service indication is transmitted between the mobiletelephone and the base station using the ‘RRC Connection Setup Request’message, the ‘RRC Connection Setup Complete’, or the ‘UE InformationResponse’ message. It will be appreciated that the D2D serviceindication can be transmitted in any part of the above messages, forexample, in a header, payload, information element, and a protocol dataunit portion of such messages. Furthermore, any other messages, such asany suitable access stratum (AS) and/or non-access stratum (NAS) messagemay be used.

In one particular example, the mobile telephone uses a tracking areaupdate procedure to inform the network about its on-going D2D service.In this case, the D2D service indication might be included in a ‘NASTracking Area Update Request’ message sent to the base station. The basestation obtains the D2D service indication from the NAS message beforeforwarding it to the Home Subscriber Server (HSS) to which it isaddressed. In this case, authorisation of the D2D service might be added(e.g. by the base station) in a ‘NAS Tracking Area Update Accept’message that is sent back to the mobile telephone by the HSS.

In another example, the request sent at step s601 configures cell signalmeasurements for the mobile telephone. In this case, step s603 comprisescell signal measurements, and step s605 comprises a cell signalreporting as specified in section 5.5 of the RRC protocol standard (3GPPTS 36.331 v11.0.0).

In yet another example, an NAS UL message or an existing UE indicationRRC UL message (e.g. IDC indication, DDA indication or MBMS indication)is adapted to include the D2D service indication and/or theauthorisation of the on-going D2D service.

In one particularly advantageous alternative, the base station obtainsindications (e.g. cell signal measurements or the like) from a pluralityof mobile telephones. Using the indications obtained from multiplesources (which might also include other network entities), the basestation works out whether or not there is an on-going (unauthorised) D2Dservice within one of its cells. In this case, parts of the D2D serviceindication are provided by different mobile telephones and/or networkentities.

In the above embodiments, the mobile telephone provided a D2D serviceindication immediately upon connecting to the base station of a detectedcellular network (i.e. in steps s405/s405′ and s505/s505′). However, itwill be appreciated that this base station might have already addressedany interference caused by the on-going D2D service (e.g. based on aninterference/D2D service indication received from another mobiletelephone as illustrated in FIG. 6) before the mobile telephoneestablishes an RRC connection. Therefore, before sending any D2Dindication to its serving base station, the mobile telephone which isinvolved in a D2D service might take into account whether or not thereis still any interference caused to (or suffered from) the othercommunication nodes served by this base station. For example, the mobiletelephone might perform cell signal measurements over the frequenciesused by the D2D service. In case the mobile telephone does not detectany interference, or it can address the interference without involvingthe network (e.g. by changing its transmission characteristics), it doesnot need to establish an RRC connection with the base station forindicating its on-going D2D service to the network (although it mightstill do so for other reasons). In this case, the mobile telephone willassume that the D2D service is authorised until it receives anindication to the contrary from the base station or the other mobiletelephone involved in the D2D service. This will considerably reduce thesignalling needed between the mobile telephone(s) and the base stationand will thus free up valuable system resources and save battery powerin the mobile telephones. However, when the interference cannot bereduced by the mobile telephone alone, it will proceed to indicate itson-going D2D service to the base station (i.e. steps s405/s405′ ors505/s505′).

In the above embodiments, the mobile telephones are cellular telephonesoperating in accordance with, for example, the LTE and/or TETRAstandards. Other types of user devices such as, for example, personaldigital assistants, laptop computers, web browsers, etc could be used.

Although the setting up of D2D communication paths have been describedbetween mobile telephones within the same communication network, the D2Dcommunication paths according to the invention may be set up betweenmobile telephones located in different communication networks. In thiscase, the mobility management entities (and in some cases the basestations) for the respective mobile telephones are also located indifferent networks.

In the above description, the base station 5 and the mobile telephones 3are described for ease of understanding as having a number of discretefunctional components or modules. Whilst these modules may be providedin this way for certain applications, for example where an existingsystem has been modified to implement the invention, in otherapplications, for example in systems designed with the inventivefeatures in mind from the outset, these modules may be built into theoverall operating system or code and so these modules may not bediscernible as discrete entities.

In the above embodiments, a number of software modules were described.As those skilled in the art will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to themobility management entity or to the base station or to the mobiletelephone as a signal over a computer network, or on a recording medium.Further, the functionality performed by part or all of this software maybe performed using one or more dedicated hardware circuits. However, theuse of software modules is preferred as it facilitates the updating ofthe mobility management entity 9, the base stations 5 and the mobiletelephones 3 in order to update their functionalities.

Various other modifications will be apparent to those skilled in the artand will not be described in further detail here.

This application is based upon and claims the benefit of priority fromUnited Kingdom patent application No. 1217019.7, filed on Sep. 24, 2012,the disclosure of which is incorporated herein in its entirely byreference.

1. A mobile communication device for communicating usingdevice-to-device (D2D) communication, the mobile communication devicecomprising: means for establishing D2D communication, with anothermobile communication device; means for searching for a communicationnetwork whilst communicating with said other mobile communication deviceusing said D2D communication; means for providing, to a communicationnetwork and responsive to said communication network being found duringsaid searching, an indication that said mobile communication device isengaged in said D2D communication; means for receiving a response tosaid indication from said communication network; and wherein said mobilecommunication device is operable to continue, or not continue, said D2Dcommunication based on said response.
 2. The mobile communication deviceaccording to claim 1 wherein said means for establishing D2Dcommunication is operable to co-ordinate the presence of gaps in saidcommunication, and said searching means is operable to monitor for saidcommunication network during said gaps in said communication.
 3. Themobile communication device according to claim 1 wherein said receivingmeans is operable to receive a response comprising information forauthorising said D2D communication wherein said mobile communicationdevice is operable to continue D2D communication based on said response.4. The mobile communication device according to claim 1 wherein saidmobile communication device is operable to cease said D2D communicationin the absence of said response within a defined time period.
 5. Themobile communication device according to claim 1 wherein said responsecomprises reconfiguration information and wherein said mobilecommunication device is operable to reconfigure said D2D communicationbased on said reconfiguration information.
 6. The mobile communicationdevice according to claim 5 wherein said mobile communication device isoperable to reconfigure said D2D communication to be controlled via saidcommunication network based on said reconfiguration information.
 7. Themobile communication device according to claim 1 wherein said receivingmeans is operable to receive a response comprising informationindicating that said D2D communication has not been authorised andwherein said mobile communication device is operable to cease said D2Dcommunication based on said response.
 8. The mobile communication deviceaccording to claim 1 wherein said mobile communication device isoperable to continue said D2D communication in the absence of saidresponse.
 9. The mobile communication device according to claim 1wherein said response comprises reconfiguration information and whereinsaid mobile communication device is operable to reconfigurecommunication between said mobile communication devices to use acommunication protocol other than a D2D based communication protocolbased on said reconfiguration information.
 10. The mobile communicationdevice according to claim 9 wherein said mobile communication device isoperable to reconfigure said communication between said mobilecommunication devices to use a cellular communication protocol (e.g. along term evolution (LTE) based communication protocol).
 11. The mobilecommunication device according to claim 1 further comprising means forestablishing a connection with said communication network when saidcommunication network has been found.
 12. The mobile communicationdevice according to claim 11 wherein said means for providing anindication is operable to provide said indication as part of saidestablishing a connection.
 13. The mobile communication device accordingto claim 11 wherein said means for providing an indication is operableto provide said indication using said connection once established. 14.The mobile communication device according to claim 11 wherein said meansfor establishing a connection is operable to establish a Radio ResourceControl (RRC) protocol connection.
 15. The mobile communication deviceaccording to claim 11 wherein said means for establishing a connectionis operable to send at least one of an ‘RRC Connection Setup Request’message and an ‘RRC Connection Setup Complete’ message as part of saidestablishing a connection and said means for providing an indication isoperable to provide said indication in said at least one said ‘RRCConnection Setup Request’ message and ‘RRC Connection Setup Complete’message.
 16. The mobile communication device according to claim 1wherein said response comprises at least one RRC protocol message. 17.The mobile communication device according to claim 16 wherein said atleast one RRC protocol message comprises at least one ‘RRC ConnectionConfiguration’ message.
 18. The mobile communication device according toclaim 1 wherein said indication providing means is operable to providefurther information identifying at least one of: a channel and/or afrequency used by said D2D communication; an interference level; anamount of data to be transmitted using said D2D communication; apriority level of said D2D communication; said mobile communicationdevice; and/or said other mobile communication device.
 19. The mobilecommunication device according to claim 18 wherein said furtherinformation is provided in response to receiving a request from a nodeof said communication network.
 20. The mobile communication deviceaccording to claim 1 wherein the mobile communication device is one of amobile telephone, a laptop computer, and a personal digital assistant.21. A communication node in a communication network for controlling amobile communication device engaged in a device-to-device (D2D)communication, the communication node comprising: means for obtaining anindication that said mobile communication device is engaged in D2Dcommunication; means for determining, based on said obtained indication,whether or not said D2D communication should be authorised; and meansfor providing to said mobile communication device, in response to saidindication, information indicating that said D2D communication has beenauthorised or information indicating that said D2D communication has notbeen authorised.
 22. The communication node according to claim 21further comprising means for configuring said mobile communicationdevice.
 23. The communication node according to claim 22 wherein saidconfiguring means is operable to reconfigure said D2D communication tobe controlled via said communication network.
 24. The communication nodeaccording to claim 22 wherein said configuring means is operable toreconfigure said communication between said mobile communication devicesto use a communication protocol other than a D2D based communicationprotocol.
 25. The communication node according to claim 24 wherein saidconfiguring means is operable to reconfigure said communication betweensaid mobile communication devices to use a cellular communicationprotocol (e.g. a long term evolution (LTE) based communicationprotocol).
 26. The communication node according to claim 21 furthercomprising means for establishing a connection with said mobilecommunication device and wherein said obtaining means is operable toobtain said indication during or after said establishment of saidconnection.
 27. The communication node according to claim 21 whereinsaid obtaining means is operable to obtain, from at least one othercommunication node connected to said communication node, informationrelating to said D2D communication.
 28. The communication node accordingto claim 27 wherein said obtaining means is operable to obtaininformation data relating to said D2D communication before saidestablishment of said radio connection.
 29. The communication nodeaccording to claim 21 wherein said obtaining means is operable to obtaininformation relating to a level of interference resulting from said D2Dcommunication and wherein said determining means determines that saidD2D communication should not be authorised when said level ofinterference is above a predetermined threshold.
 30. The communicationnode according to claim 21 wherein said obtaining means is operable toestablish a Radio Resource Control (RRC) protocol connection with saidmobile communication device and/or another mobile communication device.31. The communication node according to claim 30 wherein said obtainingmeans is operable to receive at least one RRC protocol message.
 32. Thecommunication node according to claim 31 wherein said at least one RRCprotocol message comprises at least one of an ‘RRC Connection SetupRequest’ message and an ‘RRC Connection Setup Complete’ message and saidmeans for obtaining an indication is operable to obtain said indicationfrom said at least one said ‘RRC Connection Setup Request’ message and‘RRC Connection Setup Complete’ message.
 33. The communication nodeaccording to claim 21 wherein said providing means is operable to sendat least one RRC protocol message.
 34. The communication node accordingto claim 33 wherein said at least one RRC protocol message comprises atleast one ‘RRC Connection Configuration’ or ‘RRC ConnectionReconfiguration’ message.
 35. The communication node according to claim21 further comprising means for obtaining information related to saidD2D communication from at least one of: said mobile communication deviceengaged in said D2D communication; another mobile communication devicewhich is not engaged in said D2D communication; and anothercommunication node in said communication network.
 36. The communicationnode according to claim 35 wherein said means for obtaining informationrelated to said D2D communication is operable to send a request andreceive a response to said request.
 37. The communication node accordingto claim 21 wherein said communication node is one of a base station, amobility management entity, and a home subscriber server.
 38. A mobilecommunication device for assisting a communication node managing radiochannels used by a device-to-device (D2D) communication, the mobilecommunication device comprising: means for monitoring radiotransmissions indicative of a possible D2D communication between othermobile communication devices; and means for providing informationrelating to said possible D2D communication to said communication nodeand responsive to said monitoring means detecting radio transmissionsindicative of said possible D2D communication.
 39. The mobilecommunication device according to claim 38 wherein said mobilecommunication device is operable to perform said monitoring in responseto a request form the communication node.
 40. The mobile communicationdevice according to claim 38 further comprising means for establishingD2D communication, with another mobile communication device.
 41. Asystem comprising the mobile communication device of claim
 1. 42. Amethod performed by a mobile communication device for communicatingusing device-to-device (D2D) communication, the method comprising:establishing D2D communication, with another mobile communicationdevice; searching for a communication network whilst communicating withsaid other mobile communication device using said D2D communication;providing, to a communication network and responsive to saidcommunication network being found during said searching, an indicationthat said mobile communication device is engaged in said D2Dcommunication; receiving a response to said indication from saidcommunication network; and wherein said mobile communication devicecontinues, or does not continue, said D2D communication based on saidresponse.
 43. A method performed by a communication node in acommunication network for controlling a mobile communication deviceengaged in a device-to-device (D2D) communication, the methodcomprising: obtaining an indication that said mobile communicationdevice is engaged in D2D communication; determining, based on saidobtained indication, whether or not said D2D communication should beauthorised; and providing to said mobile communication device, inresponse to said indication, information indicating that said D2Dcommunication has been authorised or information indicating that saidD2D communication has not been authorised.
 44. A method performed by amobile communication device for assisting a communication node managingradio channels used by a device-to-device (D2D) communication, themethod comprising: monitoring radio transmissions indicative of apossible D2D communication between other mobile communication devices;and providing information relating to said possible D2D communication tosaid communication node and responsive to said monitoring step detectingradio transmissions indicative of said possible D2D communication.
 45. Acomputer program product comprising computer implementable instructionsfor causing a programmable computer device to become configured as themobile communication device of claim 1.